div#container {
position: relative;
margin: 0 auto;
width: 680px;
height: 310px;
text-align: left;
}

div#left {
position: absolute;
top: 0px;
left: 0px;
width: 340px;
height: 310px;
}

div#main {
position: absolute;
top: 0px;
left: 340px;
width: 340px;
height: 310px;
}